1. Field of the Invention
The present invention relates to a structure of seat back of a vehicle seat, wherein the seat back is provided, at the back side thereof, with a back board which can serve as a load-carrying platform or cargo loading area in a vehicle.
2. Description of Prior Art
Among various kinds of seats, there is known a fold-down rear seat of the type allowing its seat back to be foldable onto its seat cushion, thereby allowing the back side of the seat back to be transformed into a load-carrying platform area in a cabin section or a cargo loading section in a vehicle cabin, as found in a recreational vehicle, a mini-van, a station wagon, a small-sized vehicle, or the like.
In most cases, this sort of fold-down rear seat is provided with a back board at the back side thereof. One typical example of such back board is known from the Japanese Laid-Open Patent Publication No. 2000-125796, according to which, one piece of robust flat panel having a high rigidity is disclosed.
Normally, a cabin or a cargo loading section in vehicle, which can accommodate the fold-down rear seat of the foregoing type, requires formation of a storage space in the floor so as to allow both of seat cushion and seat back of the seat to be stored in that storage space, such that, when the seat back is folded down onto the seat cushion, the back side of the seat back is set in registry with the upper surface of the floor. In view of such structural requirement, it is desirable that a whole of the seat, or, particularly the seat back, should be made small in thickness. Particularly, the same goes for a small-sized vehicle.
Certainly, there has been known a seat back of the type allowing its thickness to be reduced. For example, the Japanese Laid-Open Patent Pub. No. 11-192138 discloses a seat back wherein an elastic sheet element is provided on a rigid back board, thereby realizing a relatively thin back support surface provided with elastic and cushiony property, on which the back or upper body potion of the passenger is resiliently supported.
However, even such conventional thin seat back has been found defective in that a degree of elasticity of the elastic sheet element is limited by the rigid back board, resulting in a poor cushioning effect. In other words, a passenger resting on the seat back will feel, at his or her back, the hardness of the back board, due to the reduced thickness of the elastic sheet element in the seat back, with the result that a satisfactory comfortable seating touch is not attained.
In view of the above-stated drawbacks, it is a purpose of the present invention to provide an improved seat back structure of vehicle seat which not only permits its use as a load-carrying platform, but also permits a reduced thickness thereof, while retaining a high cushiony effect as a seat.
In order to achieve such purpose, in accordance with the present invention, there is basically provided a seat back structure of vehicle seat, in which the seat back has one side to supportively receive a back of an occupant on the vehicle seat and another side opposite to that one side, comprising:
an elastic back support means provided in the foregoing one side of the seat back, the elastic back support means being adapted for resiliently supporting the back of the occupant;
a back board means provided in the foregoing another side of the seat back, the back board means having: one side facing to the aforesaid one side of the seat back; and another side facing to the aforesaid another side of the seat back;
a movable connection means for connecting the elastic back support means and back board means with the seat back so as to allow displacement of the back board means in a direction from a home position to one of those one and another sides of the seat back, while allowing the elastic back support means to be resiliently warped in a direction to the afore-said one of the afore-said one and another sides of the seat back;
a stopper means for preventing movement of the back board means from the home position toward the afore-said another side of the seat back, and
a biasing means for normally biasing the back board means to the home position;
wherein the back board means is retained by the stopper means at the home position, thereby withstanding a first load applied to the foregoing another side of back board means and allowing the back board means to be usable as a means for carrying load and cargo thereon, and wherein, by contrast, when a second load is applied in a direction to the foregoing one side of seat back, the elastic back support means is resiliently warped toward that particular one side of the back board means, which in turn causes the back board means to displace toward the same another side of seat back against a biasing force of the biasing means, so that both elastic back support means and back board means are resiliently displaced toward the said another side of the seat back.
Preferably, the elastic back support means may comprise an elastic member of a substantially thin-plate configuration and the back board means may be connected with the back support means.
Preferably, the back board means may comprise a plurality of separate plate elements which are movably connected with one another in such a manner that, when the second load is applied toward the foregoing one side of the seat back, the plurality of separate plate elements are deformed and warped toward the foregoing another side of the seat back against the biasing force of the biasing means, while by contrast, when the first load is applied toward the foregoing another side of the seat back, the plurality of separate plate elements are engaged with one another to provide a robust continuous plane and retained by the stopper means at the home position so as to withstand the first load and thereby be usable as a means for carrying load and cargo on the robust continuous plane.
Other various features and advantages of the present invention will become apparent from reading of the descriptions hereinafter, with reference to the annexed drawings.